You seem to be comparing them inaccurately. You are putting Blender (as a modeling program) on the same level as PAS (which is a game engine). Yes I know that Blender has a game engine, but it's not on Sandbox' level imo.

Your last comment leads me to believe that you don't completely realize that you can use Blender with Sandbox in the same way you can use Blender with Unity. Blender is a modeling program, made be used with game engines (as part of it's purpose). Therefore, the question isn't really between Sandbox and Blender, but between actual game engines.

if you're looking to make a game for your Xbox, then you may want to look into other options, as I don't know if Blender or Sandbox would work on an Xbox. Sandbox is very easy to use, and it's pretty flexible, but I think it's kind of limited to PC. Blender is a lot harder to use, but also has options for saving and loading games, I think, and it can be ported to iOS (possibly).

It's been said a thousand times over; Sandbox is as good as your ability to make it better.

Being open-source, you could hypothetically develop it into the world's most powerful game engine, at no cost. (Other engines at Sandbox's/Cube2's level are generally very pricey, and not open source.)

However, speaking of purely native functions, Sanxbox has co-op editing, which on some projects is what sells Sandbox.

Sandbox also is fairly quick engine-wise depending on the type of game you're making.

Coming from someone who has done years of engine comparing, every engine has it's pro's and it's cons, it's very hard to say if one engine is better than another.

If you want to make maps Sandbox-style (IE, within the engine itself and in "real time"), go with Sandbox. If you want to make maps by 3D modelling every single detail of the map, go with something else.

As far as my research goes, Sandbox is the only engine I've found that natively support caves as well. Other engines you have to model the cave walls. ._.

(Although if you're an adequate modeler than these aren't major concerns.)